1/* 2 * Linux/PA-RISC Project (http://www.parisc-linux.org/) 3 * 4 * System call entry code / Linux gateway page 5 * Copyright (c) Matthew Wilcox 1999 <willy@infradead.org> 6 * Licensed under the GNU GPL. 7 * thanks to Philipp Rumpf, Mike Shaver and various others 8 * sorry about the wall, puffin.. 9 */ 10 11/* 12How does the Linux gateway page on PA-RISC work? 13------------------------------------------------ 14The Linux gateway page on PA-RISC is "special". 15It actually has PAGE_GATEWAY bits set (this is linux terminology; in parisc 16terminology it's Execute, promote to PL0) in the page map. So anything 17executing on this page executes with kernel level privilege (there's more to it 18than that: to have this happen, you also have to use a branch with a ,gate 19completer to activate the privilege promotion). The upshot is that everything 20that runs on the gateway page runs at kernel privilege but with the current 21user process address space (although you have access to kernel space via %sr2). 22For the 0x100 syscall entry, we redo the space registers to point to the kernel 23address space (preserving the user address space in %sr3), move to wide mode if 24required, save the user registers and branch into the kernel syscall entry 25point. For all the other functions, we execute at kernel privilege but don't 26flip address spaces. The basic upshot of this is that these code snippets are 27executed atomically (because the kernel can't be pre-empted) and they may 28perform architecturally forbidden (to PL3) operations (like setting control 29registers). 30*/ 31 32 33#include <asm/asm-offsets.h> 34#include <asm/unistd.h> 35#include <asm/errno.h> 36#include <asm/page.h> 37#include <asm/psw.h> 38#include <asm/thread_info.h> 39#include <asm/assembly.h> 40#include <asm/processor.h> 41#include <asm/cache.h> 42 43#include <linux/linkage.h> 44 45 /* We fill the empty parts of the gateway page with 46 * something that will kill the kernel or a 47 * userspace application. 48 */ 49#define KILL_INSN break 0,0 50 51 .level PA_ASM_LEVEL 52 53 .text 54 55 .import syscall_exit,code 56 .import syscall_exit_rfi,code 57 58 /* Linux gateway page is aliased to virtual page 0 in the kernel 59 * address space. Since it is a gateway page it cannot be 60 * dereferenced, so null pointers will still fault. We start 61 * the actual entry point at 0x100. We put break instructions 62 * at the beginning of the page to trap null indirect function 63 * pointers. 64 */ 65 66 .align PAGE_SIZE 67ENTRY(linux_gateway_page) 68 69 /* ADDRESS 0x00 to 0xb0 = 176 bytes / 4 bytes per insn = 44 insns */ 70 .rept 44 71 KILL_INSN 72 .endr 73 74 /* ADDRESS 0xb0 to 0xb8, lws uses two insns for entry */ 75 /* Light-weight-syscall entry must always be located at 0xb0 */ 76 /* WARNING: Keep this number updated with table size changes */ 77#define __NR_lws_entries (3) 78 79lws_entry: 80 gate lws_start, %r0 /* increase privilege */ 81 depi 3, 31, 2, %r31 /* Ensure we return into user mode. */ 82 83 /* Fill from 0xb8 to 0xe0 */ 84 .rept 10 85 KILL_INSN 86 .endr 87 88 /* This function MUST be located at 0xe0 for glibc's threading 89 mechanism to work. DO NOT MOVE THIS CODE EVER! */ 90set_thread_pointer: 91 gate .+8, %r0 /* increase privilege */ 92 depi 3, 31, 2, %r31 /* Ensure we return into user mode. */ 93 be 0(%sr7,%r31) /* return to user space */ 94 mtctl %r26, %cr27 /* move arg0 to the control register */ 95 96 /* Increase the chance of trapping if random jumps occur to this 97 address, fill from 0xf0 to 0x100 */ 98 .rept 4 99 KILL_INSN 100 .endr 101 102/* This address must remain fixed at 0x100 for glibc's syscalls to work */ 103 .align LINUX_GATEWAY_ADDR 104linux_gateway_entry: 105 gate .+8, %r0 /* become privileged */ 106 mtsp %r0,%sr4 /* get kernel space into sr4 */ 107 mtsp %r0,%sr5 /* get kernel space into sr5 */ 108 mtsp %r0,%sr6 /* get kernel space into sr6 */ 109 110#ifdef CONFIG_64BIT 111 /* Store W bit on entry to the syscall in case it's a wide userland 112 * process. */ 113 ssm PSW_SM_W, %r1 114 extrd,u %r1,PSW_W_BIT,1,%r1 115 /* sp must be aligned on 4, so deposit the W bit setting into 116 * the bottom of sp temporarily */ 117 or,ev %r1,%r30,%r30 118 b,n 1f 119 /* The top halves of argument registers must be cleared on syscall 120 * entry from narrow executable. 121 */ 122 depdi 0, 31, 32, %r26 123 depdi 0, 31, 32, %r25 124 depdi 0, 31, 32, %r24 125 depdi 0, 31, 32, %r23 126 depdi 0, 31, 32, %r22 127 depdi 0, 31, 32, %r21 1281: 129#endif 130 131 /* We use a rsm/ssm pair to prevent sr3 from being clobbered 132 * by external interrupts. 133 */ 134 mfsp %sr7,%r1 /* save user sr7 */ 135 rsm PSW_SM_I, %r0 /* disable interrupts */ 136 mtsp %r1,%sr3 /* and store it in sr3 */ 137 138 mfctl %cr30,%r1 139 xor %r1,%r30,%r30 /* ye olde xor trick */ 140 xor %r1,%r30,%r1 141 xor %r1,%r30,%r30 142 143 ldo THREAD_SZ_ALGN+FRAME_SIZE(%r30),%r30 /* set up kernel stack */ 144 145 /* N.B.: It is critical that we don't set sr7 to 0 until r30 146 * contains a valid kernel stack pointer. It is also 147 * critical that we don't start using the kernel stack 148 * until after sr7 has been set to 0. 149 */ 150 151 mtsp %r0,%sr7 /* get kernel space into sr7 */ 152 ssm PSW_SM_I, %r0 /* enable interrupts */ 153 STREGM %r1,FRAME_SIZE(%r30) /* save r1 (usp) here for now */ 154 mfctl %cr30,%r1 /* get task ptr in %r1 */ 155 LDREG TI_TASK(%r1),%r1 156 157 /* Save some registers for sigcontext and potential task 158 switch (see entry.S for the details of which ones are 159 saved/restored). TASK_PT_PSW is zeroed so we can see whether 160 a process is on a syscall or not. For an interrupt the real 161 PSW value is stored. This is needed for gdb and sys_ptrace. */ 162 STREG %r0, TASK_PT_PSW(%r1) 163 STREG %r2, TASK_PT_GR2(%r1) /* preserve rp */ 164 STREG %r19, TASK_PT_GR19(%r1) 165 166 LDREGM -FRAME_SIZE(%r30), %r2 /* get users sp back */ 167#ifdef CONFIG_64BIT 168 extrd,u %r2,63,1,%r19 /* W hidden in bottom bit */ 169#if 0 170 xor %r19,%r2,%r2 /* clear bottom bit */ 171 depd,z %r19,1,1,%r19 172 std %r19,TASK_PT_PSW(%r1) 173#endif 174#endif 175 STREG %r2, TASK_PT_GR30(%r1) /* ... and save it */ 176 177 STREG %r20, TASK_PT_GR20(%r1) /* Syscall number */ 178 STREG %r21, TASK_PT_GR21(%r1) 179 STREG %r22, TASK_PT_GR22(%r1) 180 STREG %r23, TASK_PT_GR23(%r1) /* 4th argument */ 181 STREG %r24, TASK_PT_GR24(%r1) /* 3rd argument */ 182 STREG %r25, TASK_PT_GR25(%r1) /* 2nd argument */ 183 STREG %r26, TASK_PT_GR26(%r1) /* 1st argument */ 184 STREG %r27, TASK_PT_GR27(%r1) /* user dp */ 185 STREG %r28, TASK_PT_GR28(%r1) /* return value 0 */ 186 STREG %r0, TASK_PT_ORIG_R28(%r1) /* don't prohibit restarts */ 187 STREG %r29, TASK_PT_GR29(%r1) /* return value 1 */ 188 STREG %r31, TASK_PT_GR31(%r1) /* preserve syscall return ptr */ 189 190 ldo TASK_PT_FR0(%r1), %r27 /* save fpregs from the kernel */ 191 save_fp %r27 /* or potential task switch */ 192 193 mfctl %cr11, %r27 /* i.e. SAR */ 194 STREG %r27, TASK_PT_SAR(%r1) 195 196 loadgp 197 198#ifdef CONFIG_64BIT 199 ldo -16(%r30),%r29 /* Reference param save area */ 200 copy %r19,%r2 /* W bit back to r2 */ 201#else 202 /* no need to save these on stack in wide mode because the first 8 203 * args are passed in registers */ 204 stw %r22, -52(%r30) /* 5th argument */ 205 stw %r21, -56(%r30) /* 6th argument */ 206#endif 207 208 /* Are we being ptraced? */ 209 mfctl %cr30, %r1 210 LDREG TI_FLAGS(%r1),%r1 211 ldi _TIF_SYSCALL_TRACE_MASK, %r19 212 and,COND(=) %r1, %r19, %r0 213 b,n .Ltracesys 214 215 /* Note! We cannot use the syscall table that is mapped 216 nearby since the gateway page is mapped execute-only. */ 217 218#ifdef CONFIG_64BIT 219 ldil L%sys_call_table, %r1 220 or,= %r2,%r2,%r2 221 addil L%(sys_call_table64-sys_call_table), %r1 222 ldo R%sys_call_table(%r1), %r19 223 or,= %r2,%r2,%r2 224 ldo R%sys_call_table64(%r1), %r19 225#else 226 load32 sys_call_table, %r19 227#endif 228 comiclr,>> __NR_Linux_syscalls, %r20, %r0 229 b,n .Lsyscall_nosys 230 231 LDREGX %r20(%r19), %r19 232 233 /* If this is a sys_rt_sigreturn call, and the signal was received 234 * when not in_syscall, then we want to return via syscall_exit_rfi, 235 * not syscall_exit. Signal no. in r20, in_syscall in r25 (see 236 * trampoline code in signal.c). 237 */ 238 ldi __NR_rt_sigreturn,%r2 239 comb,= %r2,%r20,.Lrt_sigreturn 240.Lin_syscall: 241 ldil L%syscall_exit,%r2 242 be 0(%sr7,%r19) 243 ldo R%syscall_exit(%r2),%r2 244.Lrt_sigreturn: 245 comib,<> 0,%r25,.Lin_syscall 246 ldil L%syscall_exit_rfi,%r2 247 be 0(%sr7,%r19) 248 ldo R%syscall_exit_rfi(%r2),%r2 249 250 /* Note! Because we are not running where we were linked, any 251 calls to functions external to this file must be indirect. To 252 be safe, we apply the opposite rule to functions within this 253 file, with local labels given to them to ensure correctness. */ 254 255.Lsyscall_nosys: 256syscall_nosys: 257 ldil L%syscall_exit,%r1 258 be R%syscall_exit(%sr7,%r1) 259 ldo -ENOSYS(%r0),%r28 /* set errno */ 260 261 262/* Warning! This trace code is a virtual duplicate of the code above so be 263 * sure to maintain both! */ 264.Ltracesys: 265tracesys: 266 /* Need to save more registers so the debugger can see where we 267 * are. This saves only the lower 8 bits of PSW, so that the C 268 * bit is still clear on syscalls, and the D bit is set if this 269 * full register save path has been executed. We check the D 270 * bit on syscall_return_rfi to determine which registers to 271 * restore. An interrupt results in a full PSW saved with the 272 * C bit set, a non-straced syscall entry results in C and D clear 273 * in the saved PSW. 274 */ 275 ldo -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1 /* get task ptr */ 276 LDREG TI_TASK(%r1), %r1 277 ssm 0,%r2 278 STREG %r2,TASK_PT_PSW(%r1) /* Lower 8 bits only!! */ 279 mfsp %sr0,%r2 280 STREG %r2,TASK_PT_SR0(%r1) 281 mfsp %sr1,%r2 282 STREG %r2,TASK_PT_SR1(%r1) 283 mfsp %sr2,%r2 284 STREG %r2,TASK_PT_SR2(%r1) 285 mfsp %sr3,%r2 286 STREG %r2,TASK_PT_SR3(%r1) 287 STREG %r2,TASK_PT_SR4(%r1) 288 STREG %r2,TASK_PT_SR5(%r1) 289 STREG %r2,TASK_PT_SR6(%r1) 290 STREG %r2,TASK_PT_SR7(%r1) 291 STREG %r2,TASK_PT_IASQ0(%r1) 292 STREG %r2,TASK_PT_IASQ1(%r1) 293 LDREG TASK_PT_GR31(%r1),%r2 294 STREG %r2,TASK_PT_IAOQ0(%r1) 295 ldo 4(%r2),%r2 296 STREG %r2,TASK_PT_IAOQ1(%r1) 297 ldo TASK_REGS(%r1),%r2 298 /* reg_save %r2 */ 299 STREG %r3,PT_GR3(%r2) 300 STREG %r4,PT_GR4(%r2) 301 STREG %r5,PT_GR5(%r2) 302 STREG %r6,PT_GR6(%r2) 303 STREG %r7,PT_GR7(%r2) 304 STREG %r8,PT_GR8(%r2) 305 STREG %r9,PT_GR9(%r2) 306 STREG %r10,PT_GR10(%r2) 307 STREG %r11,PT_GR11(%r2) 308 STREG %r12,PT_GR12(%r2) 309 STREG %r13,PT_GR13(%r2) 310 STREG %r14,PT_GR14(%r2) 311 STREG %r15,PT_GR15(%r2) 312 STREG %r16,PT_GR16(%r2) 313 STREG %r17,PT_GR17(%r2) 314 STREG %r18,PT_GR18(%r2) 315 /* Finished saving things for the debugger */ 316 317 copy %r2,%r26 318 ldil L%do_syscall_trace_enter,%r1 319 ldil L%tracesys_next,%r2 320 be R%do_syscall_trace_enter(%sr7,%r1) 321 ldo R%tracesys_next(%r2),%r2 322 323tracesys_next: 324 /* do_syscall_trace_enter either returned the syscallno, or -1L, 325 * so we skip restoring the PT_GR20 below, since we pulled it from 326 * task->thread.regs.gr[20] above. 327 */ 328 copy %ret0,%r20 329 330 ldo -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1 /* get task ptr */ 331 LDREG TI_TASK(%r1), %r1 332 LDREG TASK_PT_GR28(%r1), %r28 /* Restore return value */ 333 LDREG TASK_PT_GR26(%r1), %r26 /* Restore the users args */ 334 LDREG TASK_PT_GR25(%r1), %r25 335 LDREG TASK_PT_GR24(%r1), %r24 336 LDREG TASK_PT_GR23(%r1), %r23 337 LDREG TASK_PT_GR22(%r1), %r22 338 LDREG TASK_PT_GR21(%r1), %r21 339#ifdef CONFIG_64BIT 340 ldo -16(%r30),%r29 /* Reference param save area */ 341#else 342 stw %r22, -52(%r30) /* 5th argument */ 343 stw %r21, -56(%r30) /* 6th argument */ 344#endif 345 346 cmpib,COND(=),n -1,%r20,tracesys_exit /* seccomp may have returned -1 */ 347 comiclr,>> __NR_Linux_syscalls, %r20, %r0 348 b,n .Ltracesys_nosys 349 350 /* Note! We cannot use the syscall table that is mapped 351 nearby since the gateway page is mapped execute-only. */ 352 353#ifdef CONFIG_64BIT 354 LDREG TASK_PT_GR30(%r1), %r19 /* get users sp back */ 355 extrd,u %r19,63,1,%r2 /* W hidden in bottom bit */ 356 357 ldil L%sys_call_table, %r1 358 or,= %r2,%r2,%r2 359 addil L%(sys_call_table64-sys_call_table), %r1 360 ldo R%sys_call_table(%r1), %r19 361 or,= %r2,%r2,%r2 362 ldo R%sys_call_table64(%r1), %r19 363#else 364 load32 sys_call_table, %r19 365#endif 366 367 LDREGX %r20(%r19), %r19 368 369 /* If this is a sys_rt_sigreturn call, and the signal was received 370 * when not in_syscall, then we want to return via syscall_exit_rfi, 371 * not syscall_exit. Signal no. in r20, in_syscall in r25 (see 372 * trampoline code in signal.c). 373 */ 374 ldi __NR_rt_sigreturn,%r2 375 comb,= %r2,%r20,.Ltrace_rt_sigreturn 376.Ltrace_in_syscall: 377 ldil L%tracesys_exit,%r2 378 be 0(%sr7,%r19) 379 ldo R%tracesys_exit(%r2),%r2 380 381.Ltracesys_nosys: 382 ldo -ENOSYS(%r0),%r28 /* set errno */ 383 384 /* Do *not* call this function on the gateway page, because it 385 makes a direct call to syscall_trace. */ 386 387tracesys_exit: 388 ldo -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1 /* get task ptr */ 389 LDREG TI_TASK(%r1), %r1 390#ifdef CONFIG_64BIT 391 ldo -16(%r30),%r29 /* Reference param save area */ 392#endif 393 ldo TASK_REGS(%r1),%r26 394 BL do_syscall_trace_exit,%r2 395 STREG %r28,TASK_PT_GR28(%r1) /* save return value now */ 396 ldo -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1 /* get task ptr */ 397 LDREG TI_TASK(%r1), %r1 398 LDREG TASK_PT_GR28(%r1), %r28 /* Restore return val. */ 399 400 ldil L%syscall_exit,%r1 401 be,n R%syscall_exit(%sr7,%r1) 402 403.Ltrace_rt_sigreturn: 404 comib,<> 0,%r25,.Ltrace_in_syscall 405 ldil L%tracesys_sigexit,%r2 406 be 0(%sr7,%r19) 407 ldo R%tracesys_sigexit(%r2),%r2 408 409tracesys_sigexit: 410 ldo -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1 /* get task ptr */ 411 LDREG TI_TASK(%r1), %r1 412#ifdef CONFIG_64BIT 413 ldo -16(%r30),%r29 /* Reference param save area */ 414#endif 415 BL do_syscall_trace_exit,%r2 416 ldo TASK_REGS(%r1),%r26 417 418 ldil L%syscall_exit_rfi,%r1 419 be,n R%syscall_exit_rfi(%sr7,%r1) 420 421 422 /********************************************************* 423 32/64-bit Light-Weight-Syscall ABI 424 425 * - Indicates a hint for userspace inline asm 426 implementations. 427 428 Syscall number (caller-saves) 429 - %r20 430 * In asm clobber. 431 432 Argument registers (caller-saves) 433 - %r26, %r25, %r24, %r23, %r22 434 * In asm input. 435 436 Return registers (caller-saves) 437 - %r28 (return), %r21 (errno) 438 * In asm output. 439 440 Caller-saves registers 441 - %r1, %r27, %r29 442 - %r2 (return pointer) 443 - %r31 (ble link register) 444 * In asm clobber. 445 446 Callee-saves registers 447 - %r3-%r18 448 - %r30 (stack pointer) 449 * Not in asm clobber. 450 451 If userspace is 32-bit: 452 Callee-saves registers 453 - %r19 (32-bit PIC register) 454 455 Differences from 32-bit calling convention: 456 - Syscall number in %r20 457 - Additional argument register %r22 (arg4) 458 - Callee-saves %r19. 459 460 If userspace is 64-bit: 461 Callee-saves registers 462 - %r27 (64-bit PIC register) 463 464 Differences from 64-bit calling convention: 465 - Syscall number in %r20 466 - Additional argument register %r22 (arg4) 467 - Callee-saves %r27. 468 469 Error codes returned by entry path: 470 471 ENOSYS - r20 was an invalid LWS number. 472 473 *********************************************************/ 474lws_start: 475 476#ifdef CONFIG_64BIT 477 ssm PSW_SM_W, %r1 478 extrd,u %r1,PSW_W_BIT,1,%r1 479 /* sp must be aligned on 4, so deposit the W bit setting into 480 * the bottom of sp temporarily */ 481 or,ev %r1,%r30,%r30 482 483 /* Clip LWS number to a 32-bit value for 32-bit processes */ 484 depdi 0, 31, 32, %r20 485#endif 486 487 /* Is the lws entry number valid? */ 488 comiclr,>> __NR_lws_entries, %r20, %r0 489 b,n lws_exit_nosys 490 491 /* Load table start */ 492 ldil L%lws_table, %r1 493 ldo R%lws_table(%r1), %r28 /* Scratch use of r28 */ 494 LDREGX %r20(%sr2,r28), %r21 /* Scratch use of r21 */ 495 496 /* Jump to lws, lws table pointers already relocated */ 497 be,n 0(%sr2,%r21) 498 499lws_exit_nosys: 500 ldo -ENOSYS(%r0),%r21 /* set errno */ 501 /* Fall through: Return to userspace */ 502 503lws_exit: 504#ifdef CONFIG_64BIT 505 /* decide whether to reset the wide mode bit 506 * 507 * For a syscall, the W bit is stored in the lowest bit 508 * of sp. Extract it and reset W if it is zero */ 509 extrd,u,*<> %r30,63,1,%r1 510 rsm PSW_SM_W, %r0 511 /* now reset the lowest bit of sp if it was set */ 512 xor %r30,%r1,%r30 513#endif 514 be,n 0(%sr7, %r31) 515 516 517 518 /*************************************************** 519 Implementing 32bit CAS as an atomic operation: 520 521 %r26 - Address to examine 522 %r25 - Old value to check (old) 523 %r24 - New value to set (new) 524 %r28 - Return prev through this register. 525 %r21 - Kernel error code 526 527 If debugging is DISabled: 528 529 %r21 has the following meanings: 530 531 EAGAIN - CAS is busy, ldcw failed, try again. 532 EFAULT - Read or write failed. 533 534 If debugging is enabled: 535 536 EDEADLOCK - CAS called recursively. 537 EAGAIN && r28 == 1 - CAS is busy. Lock contended. 538 EAGAIN && r28 == 2 - CAS is busy. ldcw failed. 539 EFAULT - Read or write failed. 540 541 Scratch: r20, r28, r1 542 543 ****************************************************/ 544 545 /* Do not enable LWS debugging */ 546#define ENABLE_LWS_DEBUG 0 547 548 /* ELF64 Process entry path */ 549lws_compare_and_swap64: 550#ifdef CONFIG_64BIT 551 b,n lws_compare_and_swap 552#else 553 /* If we are not a 64-bit kernel, then we don't 554 * have 64-bit input registers, and calling 555 * the 64-bit LWS CAS returns ENOSYS. 556 */ 557 b,n lws_exit_nosys 558#endif 559 560 /* ELF32 Process entry path */ 561lws_compare_and_swap32: 562#ifdef CONFIG_64BIT 563 /* Clip all the input registers */ 564 depdi 0, 31, 32, %r26 565 depdi 0, 31, 32, %r25 566 depdi 0, 31, 32, %r24 567#endif 568 569lws_compare_and_swap: 570 /* Load start of lock table */ 571 ldil L%lws_lock_start, %r20 572 ldo R%lws_lock_start(%r20), %r28 573 574 /* Extract eight bits from r26 and hash lock (Bits 3-11) */ 575 extru %r26, 28, 8, %r20 576 577 /* Find lock to use, the hash is either one of 0 to 578 15, multiplied by 16 (keep it 16-byte aligned) 579 and add to the lock table offset. */ 580 shlw %r20, 4, %r20 581 add %r20, %r28, %r20 582 583# if ENABLE_LWS_DEBUG 584 /* 585 DEBUG, check for deadlock! 586 If the thread register values are the same 587 then we were the one that locked it last and 588 this is a recurisve call that will deadlock. 589 We *must* giveup this call and fail. 590 */ 591 ldw 4(%sr2,%r20), %r28 /* Load thread register */ 592 /* WARNING: If cr27 cycles to the same value we have problems */ 593 mfctl %cr27, %r21 /* Get current thread register */ 594 cmpb,<>,n %r21, %r28, cas_lock /* Called recursive? */ 595 b lws_exit /* Return error! */ 596 ldo -EDEADLOCK(%r0), %r21 597cas_lock: 598 cmpb,=,n %r0, %r28, cas_nocontend /* Is nobody using it? */ 599 ldo 1(%r0), %r28 /* 1st case */ 600 b lws_exit /* Contended... */ 601 ldo -EAGAIN(%r0), %r21 /* Spin in userspace */ 602cas_nocontend: 603# endif 604/* ENABLE_LWS_DEBUG */ 605 606 rsm PSW_SM_I, %r0 /* Disable interrupts */ 607 /* COW breaks can cause contention on UP systems */ 608 LDCW 0(%sr2,%r20), %r28 /* Try to acquire the lock */ 609 cmpb,<>,n %r0, %r28, cas_action /* Did we get it? */ 610cas_wouldblock: 611 ldo 2(%r0), %r28 /* 2nd case */ 612 ssm PSW_SM_I, %r0 613 b lws_exit /* Contended... */ 614 ldo -EAGAIN(%r0), %r21 /* Spin in userspace */ 615 616 /* 617 prev = *addr; 618 if ( prev == old ) 619 *addr = new; 620 return prev; 621 */ 622 623 /* NOTES: 624 This all works becuse intr_do_signal 625 and schedule both check the return iasq 626 and see that we are on the kernel page 627 so this process is never scheduled off 628 or is ever sent any signal of any sort, 629 thus it is wholly atomic from usrspaces 630 perspective 631 */ 632cas_action: 633#if defined CONFIG_SMP && ENABLE_LWS_DEBUG 634 /* DEBUG */ 635 mfctl %cr27, %r1 636 stw %r1, 4(%sr2,%r20) 637#endif 638 /* The load and store could fail */ 6391: ldw 0(%r26), %r28 640 sub,<> %r28, %r25, %r0 6412: stw %r24, 0(%r26) 642 /* Free lock */ 643 stw,ma %r20, 0(%sr2,%r20) 644#if ENABLE_LWS_DEBUG 645 /* Clear thread register indicator */ 646 stw %r0, 4(%sr2,%r20) 647#endif 648 /* Enable interrupts */ 649 ssm PSW_SM_I, %r0 650 /* Return to userspace, set no error */ 651 b lws_exit 652 copy %r0, %r21 653 6543: 655 /* Error occurred on load or store */ 656 /* Free lock */ 657 stw,ma %r20, 0(%sr2,%r20) 658#if ENABLE_LWS_DEBUG 659 stw %r0, 4(%sr2,%r20) 660#endif 661 ssm PSW_SM_I, %r0 662 b lws_exit 663 ldo -EFAULT(%r0),%r21 /* set errno */ 664 nop 665 nop 666 nop 667 nop 668 669 /* Two exception table entries, one for the load, 670 the other for the store. Either return -EFAULT. 671 Each of the entries must be relocated. */ 672 ASM_EXCEPTIONTABLE_ENTRY(1b-linux_gateway_page, 3b-linux_gateway_page) 673 ASM_EXCEPTIONTABLE_ENTRY(2b-linux_gateway_page, 3b-linux_gateway_page) 674 675 676 /*************************************************** 677 New CAS implementation which uses pointers and variable size 678 information. The value pointed by old and new MUST NOT change 679 while performing CAS. The lock only protect the value at %r26. 680 681 %r26 - Address to examine 682 %r25 - Pointer to the value to check (old) 683 %r24 - Pointer to the value to set (new) 684 %r23 - Size of the variable (0/1/2/3 for 8/16/32/64 bit) 685 %r28 - Return non-zero on failure 686 %r21 - Kernel error code 687 688 %r21 has the following meanings: 689 690 EAGAIN - CAS is busy, ldcw failed, try again. 691 EFAULT - Read or write failed. 692 693 Scratch: r20, r22, r28, r29, r1, fr4 (32bit for 64bit CAS only) 694 695 ****************************************************/ 696 697 /* ELF32 Process entry path */ 698lws_compare_and_swap_2: 699#ifdef CONFIG_64BIT 700 /* Clip the input registers. We don't need to clip %r23 as we 701 only use it for word operations */ 702 depdi 0, 31, 32, %r26 703 depdi 0, 31, 32, %r25 704 depdi 0, 31, 32, %r24 705#endif 706 707 /* Check the validity of the size pointer */ 708 subi,>>= 3, %r23, %r0 709 b,n lws_exit_nosys 710 711 /* Jump to the functions which will load the old and new values into 712 registers depending on the their size */ 713 shlw %r23, 2, %r29 714 blr %r29, %r0 715 nop 716 717 /* 8bit load */ 7184: ldb 0(%r25), %r25 719 b cas2_lock_start 7205: ldb 0(%r24), %r24 721 nop 722 nop 723 nop 724 nop 725 nop 726 727 /* 16bit load */ 7286: ldh 0(%r25), %r25 729 b cas2_lock_start 7307: ldh 0(%r24), %r24 731 nop 732 nop 733 nop 734 nop 735 nop 736 737 /* 32bit load */ 7388: ldw 0(%r25), %r25 739 b cas2_lock_start 7409: ldw 0(%r24), %r24 741 nop 742 nop 743 nop 744 nop 745 nop 746 747 /* 64bit load */ 748#ifdef CONFIG_64BIT 74910: ldd 0(%r25), %r25 75011: ldd 0(%r24), %r24 751#else 752 /* Load old value into r22/r23 - high/low */ 75310: ldw 0(%r25), %r22 75411: ldw 4(%r25), %r23 755 /* Load new value into fr4 for atomic store later */ 75612: flddx 0(%r24), %fr4 757#endif 758 759cas2_lock_start: 760 /* Load start of lock table */ 761 ldil L%lws_lock_start, %r20 762 ldo R%lws_lock_start(%r20), %r28 763 764 /* Extract eight bits from r26 and hash lock (Bits 3-11) */ 765 extru %r26, 28, 8, %r20 766 767 /* Find lock to use, the hash is either one of 0 to 768 15, multiplied by 16 (keep it 16-byte aligned) 769 and add to the lock table offset. */ 770 shlw %r20, 4, %r20 771 add %r20, %r28, %r20 772 773 rsm PSW_SM_I, %r0 /* Disable interrupts */ 774 /* COW breaks can cause contention on UP systems */ 775 LDCW 0(%sr2,%r20), %r28 /* Try to acquire the lock */ 776 cmpb,<>,n %r0, %r28, cas2_action /* Did we get it? */ 777cas2_wouldblock: 778 ldo 2(%r0), %r28 /* 2nd case */ 779 ssm PSW_SM_I, %r0 780 b lws_exit /* Contended... */ 781 ldo -EAGAIN(%r0), %r21 /* Spin in userspace */ 782 783 /* 784 prev = *addr; 785 if ( prev == old ) 786 *addr = new; 787 return prev; 788 */ 789 790 /* NOTES: 791 This all works becuse intr_do_signal 792 and schedule both check the return iasq 793 and see that we are on the kernel page 794 so this process is never scheduled off 795 or is ever sent any signal of any sort, 796 thus it is wholly atomic from usrspaces 797 perspective 798 */ 799cas2_action: 800 /* Jump to the correct function */ 801 blr %r29, %r0 802 /* Set %r28 as non-zero for now */ 803 ldo 1(%r0),%r28 804 805 /* 8bit CAS */ 80613: ldb 0(%r26), %r29 807 sub,= %r29, %r25, %r0 808 b,n cas2_end 80914: stb %r24, 0(%r26) 810 b cas2_end 811 copy %r0, %r28 812 nop 813 nop 814 815 /* 16bit CAS */ 81615: ldh 0(%r26), %r29 817 sub,= %r29, %r25, %r0 818 b,n cas2_end 81916: sth %r24, 0(%r26) 820 b cas2_end 821 copy %r0, %r28 822 nop 823 nop 824 825 /* 32bit CAS */ 82617: ldw 0(%r26), %r29 827 sub,= %r29, %r25, %r0 828 b,n cas2_end 82918: stw %r24, 0(%r26) 830 b cas2_end 831 copy %r0, %r28 832 nop 833 nop 834 835 /* 64bit CAS */ 836#ifdef CONFIG_64BIT 83719: ldd 0(%r26), %r29 838 sub,*= %r29, %r25, %r0 839 b,n cas2_end 84020: std %r24, 0(%r26) 841 copy %r0, %r28 842#else 843 /* Compare first word */ 84419: ldw 0(%r26), %r29 845 sub,= %r29, %r22, %r0 846 b,n cas2_end 847 /* Compare second word */ 84820: ldw 4(%r26), %r29 849 sub,= %r29, %r23, %r0 850 b,n cas2_end 851 /* Perform the store */ 85221: fstdx %fr4, 0(%r26) 853 copy %r0, %r28 854#endif 855 856cas2_end: 857 /* Free lock */ 858 stw,ma %r20, 0(%sr2,%r20) 859 /* Enable interrupts */ 860 ssm PSW_SM_I, %r0 861 /* Return to userspace, set no error */ 862 b lws_exit 863 copy %r0, %r21 864 86522: 866 /* Error occurred on load or store */ 867 /* Free lock */ 868 stw,ma %r20, 0(%sr2,%r20) 869 ssm PSW_SM_I, %r0 870 ldo 1(%r0),%r28 871 b lws_exit 872 ldo -EFAULT(%r0),%r21 /* set errno */ 873 nop 874 nop 875 nop 876 877 /* Exception table entries, for the load and store, return EFAULT. 878 Each of the entries must be relocated. */ 879 ASM_EXCEPTIONTABLE_ENTRY(4b-linux_gateway_page, 22b-linux_gateway_page) 880 ASM_EXCEPTIONTABLE_ENTRY(5b-linux_gateway_page, 22b-linux_gateway_page) 881 ASM_EXCEPTIONTABLE_ENTRY(6b-linux_gateway_page, 22b-linux_gateway_page) 882 ASM_EXCEPTIONTABLE_ENTRY(7b-linux_gateway_page, 22b-linux_gateway_page) 883 ASM_EXCEPTIONTABLE_ENTRY(8b-linux_gateway_page, 22b-linux_gateway_page) 884 ASM_EXCEPTIONTABLE_ENTRY(9b-linux_gateway_page, 22b-linux_gateway_page) 885 ASM_EXCEPTIONTABLE_ENTRY(10b-linux_gateway_page, 22b-linux_gateway_page) 886 ASM_EXCEPTIONTABLE_ENTRY(11b-linux_gateway_page, 22b-linux_gateway_page) 887 ASM_EXCEPTIONTABLE_ENTRY(13b-linux_gateway_page, 22b-linux_gateway_page) 888 ASM_EXCEPTIONTABLE_ENTRY(14b-linux_gateway_page, 22b-linux_gateway_page) 889 ASM_EXCEPTIONTABLE_ENTRY(15b-linux_gateway_page, 22b-linux_gateway_page) 890 ASM_EXCEPTIONTABLE_ENTRY(16b-linux_gateway_page, 22b-linux_gateway_page) 891 ASM_EXCEPTIONTABLE_ENTRY(17b-linux_gateway_page, 22b-linux_gateway_page) 892 ASM_EXCEPTIONTABLE_ENTRY(18b-linux_gateway_page, 22b-linux_gateway_page) 893 ASM_EXCEPTIONTABLE_ENTRY(19b-linux_gateway_page, 22b-linux_gateway_page) 894 ASM_EXCEPTIONTABLE_ENTRY(20b-linux_gateway_page, 22b-linux_gateway_page) 895#ifndef CONFIG_64BIT 896 ASM_EXCEPTIONTABLE_ENTRY(12b-linux_gateway_page, 22b-linux_gateway_page) 897 ASM_EXCEPTIONTABLE_ENTRY(21b-linux_gateway_page, 22b-linux_gateway_page) 898#endif 899 900 /* Make sure nothing else is placed on this page */ 901 .align PAGE_SIZE 902END(linux_gateway_page) 903ENTRY(end_linux_gateway_page) 904 905 /* Relocate symbols assuming linux_gateway_page is mapped 906 to virtual address 0x0 */ 907 908#define LWS_ENTRY(_name_) ASM_ULONG_INSN (lws_##_name_ - linux_gateway_page) 909 910 .section .rodata,"a" 911 912 .align 8 913 /* Light-weight-syscall table */ 914 /* Start of lws table. */ 915ENTRY(lws_table) 916 LWS_ENTRY(compare_and_swap32) /* 0 - ELF32 Atomic 32bit CAS */ 917 LWS_ENTRY(compare_and_swap64) /* 1 - ELF64 Atomic 32bit CAS */ 918 LWS_ENTRY(compare_and_swap_2) /* 2 - ELF32 Atomic 64bit CAS */ 919END(lws_table) 920 /* End of lws table */ 921 922#define __SYSCALL(nr, entry) ASM_ULONG_INSN entry 923 .align 8 924ENTRY(sys_call_table) 925 .export sys_call_table,data 926#ifdef CONFIG_64BIT 927#include <asm/syscall_table_c32.h> /* Compat syscalls */ 928#else 929#include <asm/syscall_table_32.h> /* 32-bit native syscalls */ 930#endif 931END(sys_call_table) 932 933#ifdef CONFIG_64BIT 934 .align 8 935ENTRY(sys_call_table64) 936#include <asm/syscall_table_64.h> /* 64-bit native syscalls */ 937END(sys_call_table64) 938#endif 939#undef __SYSCALL 940 941 /* 942 All light-weight-syscall atomic operations 943 will use this set of locks 944 945 NOTE: The lws_lock_start symbol must be 946 at least 16-byte aligned for safe use 947 with ldcw. 948 */ 949 .section .data 950 .align L1_CACHE_BYTES 951ENTRY(lws_lock_start) 952 /* lws locks */ 953 .rept 256 954 /* Keep locks aligned at 16-bytes */ 955 .word 1 956 .word 0 957 .word 0 958 .word 0 959 .endr 960END(lws_lock_start) 961 .previous 962 963.end 964 965 966